by: Dr. Paul Chang, General Practitioner, Regis Medical
Unlike immediate food allergies, which cause swift and sometimes severe reactions, delayed food sensitivities are often hidden culprits behind chronic symptoms such as fatigue, bloating, skin flare-ups, and joint pain. These sensitivities involve immune system responses that occur hours or even days after consuming a trigger food, making them difficult to detect without proper testing.
Immediate food allergies involve IgE (Immunoglobulin E) anti-bodies, which cause rapid-onset symptoms like hives, swelling, or anaphylaxis — typically within minutes to an hour.
Delayed food sensitivities involve IgG (Immunoglobulin G) antibodies and manifest subtly over time, often 12–72 hours after ingestion.
Because the immune reaction is slow and cumulative, people with IgG-mediated food sensitivities may not associate their symptoms with what they ate two days ago. This leads to ongoing exposure, chronic inflammation, and a worsening of symptoms.
When a person with a sensitivity eats a trigger food, the immune system produces IgG antibodies that bind to that food’s proteins. This immune complex can:
Skin prick tests and IgE blood panels are excellent at detecting classic allergies (like peanuts or shellfish), but they do not capture delayed IgG sensitivities. That’s why people can test “negative” for allergies but still feel unwell after eating certain foods.
Leaky gut, caused by poor diet, stress, medication (like antibiotics or NSAIDs), or infections, allows partially digested food proteins to enter the bloodstream and trigger immune responses.
Regular consumption of the same foods (like eggs, wheat, or dairy) without rotation can overwhelm the immune system over time.
Stress weakens gut barrier function and shifts the immune system into a pro-inflammatory state, increasing susceptibility to food sensitivities.
The most reliable method is an IgG food sensitivity blood test, which measures the immune system’s response to specific food proteins. This allows a clear understanding of which foods may be driving inflammation.
Other methods like elimination diets are helpful, but they:
Work with a healthcare provider or dietitian to interpret your IgG results and temporarily remove reactive foods.
Incorporate gut-supportive nutrients like:
Once inflammation subsides, some individuals may tolerate reintroducing low-reactive foods after 8–12 weeks.
Many people live with delayed food sensitivities without realising their food is the cause of their discomfort. Identifying and managing these triggers can lead to clearer skin, better digestion, improved mood and energy, and reduced inflammation.
If you're dealing with persistent symptoms, chronic fatigue, or inflammation without a clear diagnosis, it's worth exploring whether delayed food sensitivity is the missing link.
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Children’s Allergy Doctors. (n.d.). Delayed food allergy. Retrieved April 24, 2025, from https://childrensallergydoctors.com/delayed-food-allergy
Food Allergy Research and Resource Program (FARRP). (n.d.). General information on food allergies and sensitivities. University of Nebraska–Lincoln. Retrieved April 24, 2025, from https://farrp.unl.edu/farrp-resources/general-information-food-allergies-sensitivities
Healthline. (2023, May 9). What is a delayed food allergy? Retrieved April 24, 2025, from https://www.healthline.com/health/allergies/delayed-food-allergy
Liu, E., & Jaramillo, R. (2010). Food allergy and gastrointestinal manifestations. Current Opinion in Pediatrics, 22(5), 635–639. https://pubmed.ncbi.nlm.nih.gov/20978655/